1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive device which is provided with a movable section to be operated on the basis of a displacement action of a piezoelectric/electrostrictive element, or a piezoelectric/electrostrictive device which is capable of detecting displacement of a movable section by the aid of a piezoelectric/electrostrictive element, and a method for producing the same. In particular, the present invention relates to a piezoelectric/electrostrictive device which is excellent in strength, shock resistance, and moisture resistance and which makes it possible to efficiently operate a movable section to a great extent, and a method for producing the same.
2. Description of the Related Art
Recently, a displacement element, which makes it possible to adjust optical path length and position on the order of submicrons, is required, for example, in the fields of optics, magnetic recording, and precision machining. Development is advanced for the displacement element based on the use of the displacement brought about by the inverse piezoelectric effect or the electrostrictive effect caused when a voltage is applied to a piezoelectric/electrostrictive material (for example, a ferroelectric material).
As shown in FIG. 41, for example, those hitherto disclosed as such a displacement element include a piezoelectric actuator comprising a fixation section 204, a movable section 206, and a beam section 208 for supporting them which are formed in an integrated manner with a hole 202 provided through a plate-shaped member 200 composed of a piezoelectric/electrostrictive material and with an electrode layer 210 provided on the beam section 208 (see, for example, Japanese Laid-Open Patent Publication No. 10-136665).
The piezoelectric actuator is operated such that when a voltage is applied to the electrode layer 210, the beam section 208 makes expansion and contraction in a direction along a line obtained by connecting the fixation section 204 and the movable section 206 in accordance with the inverse piezoelectric effect or the electrostrictive effect. Therefore, the movable section 206 can perform circular arc-shaped displacement or rotational displacement in the plane of the plate-shaped member 200.
On the other hand, Japanese Laid-Open Patent Publication No. 63-64640 discloses a technique in relation to an actuator based on the use of a bimorph. In this technique, electrodes for the bimorph are provided in a divided manner. The actuator is driven due to the selection of the divided electrodes, and thus the highly accurate positioning is performed at a high speed. This patent document (especially in FIG. 4) discloses a structure in which, for example, two bimorphs are used in an opposed manner.
However, the piezoelectric actuator described above involves such a problem that the amount of operation of the movable section 206 is small, because the displacement in the direction of expansion and contraction of the piezoelectric/electrostrictive material (i.e., in the in-plane direction of the plate-shaped member 200) is transmitted to the movable section 206 as it is.
All, of the parts of the piezoelectric actuator are made or the piezoelectric/electrostrictive material which is a fragile material having a relatively heavy weight. Therefore, the following problems arise. That is, the mechanical strength is low, and the piezoelectric actuator is inferior in handling performance, shock resistance, and moisture resistance. Further, the piezoelectric actuator itself is heavy, and its operation tends to be affected by harmful vibrations (for example, residual vibration and noise vibration during high speed operation).
In order to solve the problems described above, it has been suggested that the hole 202 is filled with a filler material having flexibility. However, it is clear that the amount of displacement, which is brought about by the inverse piezoelectric effect or the electrostrictive effect, is decreased even when the filler material is used.
Further, the actuator described in Japanese Laid-Open Patent Publication No. 63-64640 has such a structure that the bimorph itself is composed of two piezoelectric elements which are laminated with each other, in addition to the fact that the bimorph is stuck to a fixation member or a mediating member. Therefore, the stress tends to remain, resulting from, for example, the curing and the shrinkage of an adhesive and the heating treatment required for the sticking and the lamination. It is feared that the displacement action is disturbed by the internal residual stress, and it is impossible to realize the displacement and the resonance frequency as designed. Especially, when the actuator is small in size, the influence of the adhesive is increased by itself.
Accordingly, a method is conceived in order to exclude the influence of the adhesive required to effect the sticking, in which the actuator is composed of, for example, an integrated sintered product made of ceramics to give a structure in which no adhesive is used. However, also in this case, it is inevitably feared that the internal residual stress arises due to the difference in behavior of thermal shrinkage between respective members during the sintering.
Further, when the actuator is small in size, a problem is involved such that the fixation property of the actuator and the attachment property of the actuator to another part are deficient.